Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$234.60	8.658%	$254.9117	$254.91	$254.90	$254.90
Purchase #2	$41.75	12.834%	$47.1082	$47.11	$47.10	$47.10
Purchase #3	$82.32	8.625%	$89.4201	$89.42	$89.40	$89.40
Purchase #4	$234.30	8.607%	$254.4662	$254.47	$254.45	$254.50
Purchase #5	$186.44	12.443%	$209.6387	$209.64	$209.65	$209.60
Purchase #6	$44.81	8.672%	$48.6959	$48.70	$48.70	$48.70
Purchase #7	$209.32	6.613%	$223.1623	$223.16	$223.15	$223.20
7 purchase totals =	$1,033.54		$1,127.4031	$1,127.41	$1,127.35	$1,127.40